The present invention is directed to a tamper detector such as for a utility meter and, more particularly, to a wake-up capability of a power supply of a tamper detector.
Tampering with a module such as a utility meter involves unauthorized access to the module with the intention of for example, retrieving, altering or adulterating sensitive information processed by the module. A protected object may be a secured electronic module such as a utility meter, point-of-sale (POS) terminal, terminal for use with smart cards or a cryptographic module. Security and protection counter-measures against tampering typically involve detection of attack on features making unauthorized physical access more difficult, and detection of electronic intrusion.
The tamper detector may detect interference with detection circuits securing access to the module. The detection circuits may be electrical conductors whose continuity is interrupted by tampering. Alternatively, the electrical detection circuits may have switches designed to open or close if a closure is opened, or sensors detecting acceleration or other abnormal physical changes. A passive tamper detector may apply a voltage to a detection circuit of the physical security feature and detect the current in the circuit. An active tamper detector may apply a signed detection signal to one end of the detection circuit and compare it with a signal received at the other end of the detection circuit.
Tamper detectors commonly include a real-time clock (RTC) module having an RTC oscillator that provides an RTC signal that may also be used in the protected module itself. RTC modules typically have a secondary source of power in the form of a rechargeable battery so they can continue to keep time while the primary source of power is off or unavailable. This enables the rest of the system to shut down or sleep, saving power, and also enables the RTC oscillator to function if power to the system is cut off. The RTC oscillator may provide a reference clock correcting the time registered by the system clocks.
It is desirable to reduce the vulnerability of the tamper detector to attack on the RTC module itself, for example its vulnerability to attempts to disable or deteriorate the tamper detection by removing the rechargeable battery. This might be motivated in the example of an electricity meter in order to falsify usage recorded by the meter.